Background: The range of nucleic acid-based technologies for the molecular detection of pathogens has grown rapidly in recent years. The influx of new testing methods into the clinical laboratory, demands for evaluation and standardisation of methods, interpretation of results and evaluation of laboratory performance have highlighted the need for internal and External Quality Assessment (EQA) systems more than ever before. External Quality Assessment panels demand reproducible, stable specimens of consistent form, suitable for transportation. Objectives: To determine the stability of freeze-dried viral specimens in terms of molecular detection. Study design: When EQA specimens are prepared, they undergo long-term storage and testing as part of the quality control (QC) process. The frequency and nature of testing is dependent on the resources and methodologies available at the time. A range of virus preparations used for EQA was monitored over a period of months to years in a retrospective study; the available quality monitoring data for the five viruses, including storage temperature and method of detection were analysed. Results: The nucleic acid (DNA or RNA) of the freeze-dried viruses included in the study was readily detectable over a long period of time. Quantitative analysis indicated that detectable concentrations of nucleic acid post-freeze drying were similarly maintained. Storage temperature was an important factor in the stability of HCV, but other viruses were unaffected by storage at different temperatures. Conclusions: In summary, the molecular detection of nucleic acid (DNA or RNA) in freeze-dried specimens of HSV1, HSV2, HBV, HCV and HIV is possible even after prolonged storage, in some cases at a range of temperatures. Freeze drying allows large-scale production of viral specimens of high quality for EQA, which are stable in varying storage and shipment conditions. Furthermore, detection of each virus was possible with a range of commonly used molecular diagnostic methods.
- External Quality Assessment
- Molecular detection